103 



IV. EXPEhlL'LFNT 2: THJ' PKhJLIUINABY IKCLIIffil PLi\IIE . 



The apparatus used in tiais experiment (see PlHte 

 VI) wp.s desij^neri especially to nake a problem exceptionally 

 difficult to learn, and in this purpose it succeeded beyond 

 expectation. The basic principle in the same as thwt of the 

 apparatus used by V/ataon^in his experimrnts at the Univei-si- 

 ty of Chicdi^o , described and illustrated in his monograph "An- 

 imal Education," page 37. But my apparatus differs from his 

 in several respects. 



V/atson, Animal Education, Chicago, ]903. 



Plate VI shows in detail the construction and meth- 

 od of operation. The food box. A, is framed of v/ood, 11 x 12 

 inches base, 11 inches in heijjht and covered by 3/6 inch heavy 

 v/ire mesh. It is fitted v/ith a hard rubber aoor, d, 3/16 Inch 

 thick, 5 inches high and 4 1/4 inches wide. To the door is 

 fastened a cord which passes over a pulley, p, and is \7eight- 

 ed at the other end with a piece of lead, 1, of sufficient 

 Vr-eight to insure the openint^ of the aoor upon releasing the 

 latch. B shows the device for latchint^ and releasing the door. 

 A short distance above the door is fastened a 3inch electric- 

 al magnet, m; directly belov/ that is a steel wire, s.w. , sur- 

 mounted by a steel disk, s.d., of the same diajneter. as the 

 core of the mat^net. The steel wire holds the door by dropping 

 through holes in two brass plates, g, which serve os guides, 

 to a point, behind another brnss plnte which is set at the top 

 of and behind the door, 1 1/2 i.u'i uelow the top of the door. 



